The big question in Jiujitsu - Gi or no Gi? Well the answer just isn't that simple and it really boils down to what your agenda per training is. Do you want to compete? Do you want self defense for real life scenarios? Are you looking to just get some exercise? These are the questions to ask yourself, how you answer will determine what kind of grappling you should pursue.
If you want to compete, it's best you learn both. Most jiujitsu gyms do both, even the old school BJJ fanatics are opening up to no Gi. The reason you'd want both as a competitor is because the Gi slows you down and makes you more technical, it improves your grip strength like no other. The no Gi system makes you much faster and teaches you to not rely on wrist holds and collar chokes.
If you want to learn self defense, probably best to learn both. For the same reasons as a competitor but different application. The Gi will make you focus more on technique and grip strength which translates to winning a physical encounter on the street. The no Gi will prepare you for what grappling someone in blue jeans and a T-shirt is really like.
If you just want some exercise, it really doesn't matter and just up to you at that point. You're gonna get cardio doing drills and rolling with your camp regardless. Just make sure you're in a good gym.
Above all focus on finding the best gym. Make sure your training style fits in with your coaches philosophies, as they all teach differently.